1. Field of the Invention
The present invention relates to a coordinate input device and more particularly to a coordinate input device wherein a coordinate position detected by a contact type coordinate detecting section adapted to be pushed by an operating means such as a finger can be calculated easily by an arithmetic operation performed by a coordinate position calculating circuit.
2. Description of the Related Art
Heretofore, in a signal processor such as a personal computer there has been used a coordinate input device provided with a capacitance detection type coordinate detecting section which is operated by an operating means such as a finger.
FIG. 3 is a block diagram showing an example of a schematic configuration of such a known coordinate input device.
As shown in FIG. 3, the coordinate input device illustrated therein comprises a capacitance detection type coordinate detecting section 31 having a plurality(n number) of X electrodes 3.sub.21 to 32.sub.n arranged in parallel in X-axis direction and a plurality (m number) of Y electrodes 3.sub.31 to 33.sub.m arranged in parallel in Y-axis direction, an operating means 34, for example a finger of an operator, for operating a desired coordinate position on an operating surface of the coordinate detecting section 31, a drive signal generating section 35 for providing drive signals to the X electrodes 32.sub.1 .about.32.sub.n, a position detecting section 36 which outputs as an electric current a change in capacitance of Y electrodes 33.sub.1 to 33.sub.m which is caused upon operation by the operating means 34, an arithmetic section 37 which, on the basis of the drive signals and changes in electric current, calculates the coordinate position on the operating surface of the coordinate detecting section 31 having been operated by the operating means 34 and then outputs coordinate position data, a data output section 38 which converts the coordinate position data into a signal suitable for transmission, and a control section 39 for controlling the operation of the entire coordinate input device.
The known coordinate input device constructed as above generally operates as follows.
In the capacitance detection type coordinate detecting section 31, the X electrodes 32.sub.1 to 32.sub.n are scanned successively with drive signals outputted from the drive signal generating section 35, and electric currents proportional to capacitance values in Y electrodes 33.sub.1 to 33.sub.m are detected successively by the position detecting section 36. In this state, when the operator operates a desired position on the operating surface of the coordinate detection section 31 with his or her finger 34, there occurs changes in the value of capacitance of the operated Y electrodes 33.sub.1, and the changes in capacitance are detected as changes in electric current by the position detecting section 36, which in turn outputs electric current values. In accordance with the control signal fed from the control section 39 and the electric current values provided from the position detecting section 36, the arithmetic section 37 calculates, as coordinate position data, both X and Y coordinate positions where the change in capacitance value is the largest. The data output section 38 converts the coordinate position data obtained in the arithmetic section 37 into a transmission signal suitable for transmission, which signal is then transmitted to a signal processing means(not shown) such as a personal computer through a connection line or by wireless means such as infrared light or radio.
Since the above known coordinate input device detects a delicate change in capacitance between X electrode (32.sub.1 .about.32.sub.n) and Y electrode (33.sub.1 .about.33.sub.m) upon contact therewith of the operating means 34 and then calculates coordinate position data, it requires an amplifier circuit for amplifying the change in capacitance, a processing circuit for processing against disturbance noise, and a complicated arithmetic processing circuit. Thus, there arises the problem that the manufacturing cost of the coordinate input device becomes high.